Purity analysis method for crude vinyl chloride in conversion process

Abstract

The invention discloses a purity analysis method for crude vinyl chloride in a conversion process, which comprises the following steps: after sampling, carrying out qualitative and quantitative analysis on small molecule components in the crude vinyl chloride, then analyzing acetylene and high-boiling residues in the crude vinyl chloride, and calculating the purity of the crude vinyl chloride according to a deduction method. Compared with the prior art, the aluminum foil sampling bag is adopted for sampling, so that the problem of poor sample representativeness is solved; the content of the high-boiling residues in the crude vinyl chloride can be accurately analyzed by adopting gas chromatography, so that the accuracy and precision of analysis data are improved; according to the method, gas chromatography is adopted to completely replace a dichloroethane absorption method, so that the working intensity of workers is reduced, and the method has the effects of safety, environmental protection and low energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of purity analysis of crude vinyl chloride in the chlor-alkali industry, and in particular to a purity analysis method for crude vinyl chloride in a conversion process. Background Art

[0002] In the conversion process of the chlor-alkali industry, qualified hydrogen chloride and acetylene are mixed and dehydrated in proportion, synthesized in the converter, and removed by mercury, deacidification, and alkali washing to generate crude vinyl chloride gas. In the prior art, the method for analyzing the purity of crude vinyl chloride is to use a spherical bladder for sampling, use the dichloroethane absorption method to analyze the vinyl chloride content, and use gas chromatography to analyze the acetylene content in crude vinyl chloride. The value of the difference between the two values ​​is the purity of crude vinyl chloride; when using the dichloroethane absorption method, it is necessary to operate an Ostwald gas analyzer, which has the problem of complex manual analysis operation process and low analysis accuracy and precision; in addition, during the experiment, dichloroethane is contacted, which is volatile and has an anesthetic effect when contacted for a long time. It is a toxic and harmful substance, and no non-toxic and harmless substitute can be found. When sampling, a spherical bladder is used as a sampling tool, and the reproducibility of the analysis results of the sample is poor, and the accuracy of the review results cannot be guaranteed. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a purity analysis method for crude vinyl chloride in a conversion process.

[0004] To achieve this technical purpose, the present invention adopts the following scheme: A purity analysis method for crude vinyl chloride in a conversion process comprises the following steps: The first step is to use an aluminum foil sampling bag for sampling. Before sampling, use a vacuum pump to evacuate the aluminum foil sampling bag and close the sampling bag valve to avoid the introduction of air; when sampling on site, first open the sampling valve to discharge the dead volume, then connect the aluminum foil sampling bag to the sampling valve through a soft rubber hose, open the sampling valve, fill the aluminum foil sampling bag, close the upper valve of the aluminum foil sampling bag and the on-site sampling valve, and complete the sampling work.

[0005] In the second step, chromatography is used to conduct qualitative and quantitative analysis of small molecular components such as hydrogen, oxygen, nitrogen and methane in crude vinyl chloride; Chromatographic conditions: Carrier gas: high-purity argon (purity is 99.999%); detector type: TCD; injection port temperature: 110℃; detector temperature: 250℃; column temperature: 50℃; chromatographic column: 3m stainless steel column (filled with 60-80 mesh 13X molecular sieve aged at 350℃); the total flow rate of the injection port gas is set to 5.999mL / min, and the flow rate of the septum purge gas is set to 3.0mL / min; the detector reference gas flow rate is set to 30.00mL / min, and the tail gas (nitrogen) flow rate is set to 5.0mL / min; chromatographic manufacturer: Agilent 7890B, USA; Standard gas: The volume percentage of hydrogen, oxygen, nitrogen and methane is 1.00%, and argon is used as the balance gas; Testing steps: Open the valve of the argon cylinder, control the outlet pressure to 0.4MPa through the pressure reducing valve, turn on the chromatographic host and computer, open the application, call out the method, and the chromatographic system automatically enters the heating program. When ready, edit the sample information, click OK, open the six-way valve, connect the aluminum foil sampling bag to the six-way valve, and start sampling; start running for 2 minutes; after the chromatographic operation is completed, directly read the analysis data; each sample needs to be tested repeatedly, and the average value of the two tests is taken as the final analysis result; The third step is to analyze the contents of acetylene and high-boiling components in the crude vinyl chloride by chromatography; Chromatographic conditions: Carrier gas: high-purity nitrogen (purity is 99.999%); detector type: hydrogen flame ionization detector; column temperature: using programmed temperature rise mode, maintain at 35°C for 4.9 minutes, and then increase to 240°C at a rate of 35°C per minute and maintain for 4 minutes; detector temperature is 300°C, fuel gas flow rate is 30mL / min, practical gas flow rate is 400mL / min, and tail gas flow rate is 25mL / min; injection port temperature is 150°C, flow rate is 25mL / min, and septum purge flow rate is 3mL / min; split ratio is 8:1; chromatographic column uses capillary column: DB-624, 29m×530um×3um, flow rate is 2.2mL / min; chromatographic manufacturer: Agilent 7890A, USA; Standard gas: acetylene 2.5%; vinyl chloride, methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, trichloroethylene content are 30ppm; methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane content are 60ppm, nitrogen is used as the balance gas; Testing steps: Open the valve of the nitrogen cylinder, control the outlet pressure to 0.4MPa through the pressure reducing valve, turn on the chromatographic host and computer, open the application, call out the method, the chromatogram automatically enters the heating program, and when ready, edit the sample information, click OK, use a 1ml glass syringe to draw 0.5ml of sample and inject it through the upper injection port; start the run for 7.2 minutes; after the chromatographic run is completed, directly read the analysis data; each sample needs to be tested repeatedly, and the average value of the two tests is taken as the final analysis result.

[0006] Furthermore, the standard curve was prepared using the external standard method; High boiling substances include: the sum of methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, trichloroethylene, methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane and other components; The fourth step is to use the subtraction method to subtract the contents of all components such as hydrogen, nitrogen, oxygen, methane, acetylene and high-boiling substances from 100%, and finally calculate the purity content of crude vinyl chloride.

[0007] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention adopts aluminum foil sampling bags for sampling, so the samples are easy to preserve and highly representative, ensuring that the samples can be reviewed at any time with good reproducibility; (2) The present invention adopts gas chromatography analysis, which completely replaces manual analysis, reduces the workload of workers, and improves the accuracy and precision of analysis; (3) It takes about 10 minutes to analyze the crude vinyl chloride sample by artificial absorption method; it takes about 5 minutes by gas chromatography, which saves more analysis time and has high analysis efficiency; (4) The present invention uses Agilent gas chromatography imported from the United States to analyze the high-boiling-point content in crude vinyl chloride, thereby improving the accuracy of the analysis data; domestic gas chromatography cannot achieve the same analysis accuracy; (5) The present invention analyzes multiple components of crude vinyl chloride to provide more accurate data for production. Production can check the components that affect the purity of crude vinyl chloride at any time, which is more conducive to the adjustment of production control. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is the first detection spectrum of the small molecule component in the embodiment of the present invention; Figure 2 This is the second detection spectrum of the small molecule component in the embodiment of the present invention; Figure 3 This is the first detection spectrum of acetylene and high boiling substances in the embodiment of the present invention; Figure 4 This is the second detection spectrum of acetylene and high boiling substances in the embodiment of the present invention; DETAILED DESCRIPTION

[0009] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific implementation methods, but the present invention is not limited thereto.

[0010] The present invention provides a purity analysis method for crude vinyl chloride in a conversion process, wherein gas chromatography is used to perform qualitative and quantitative analysis on small molecular components, acetylene and high boiling points in crude vinyl chloride, and a subtraction method is used to subtract the sum of all low-content components to finally obtain the purity of crude vinyl chloride. The specific analysis steps are as follows: The first step is to use an aluminum foil sampling bag for sampling. Before sampling, use a vacuum pump to evacuate the aluminum foil sampling bag and close the sampling bag valve to avoid the introduction of air; when sampling on site, first open the sampling valve to discharge the dead volume, then connect the aluminum foil sampling bag to the sampling valve through a soft rubber hose, open the sampling valve, fill the aluminum foil sampling bag, close the upper valve of the aluminum foil sampling bag and the on-site sampling valve, and complete the sampling work.

[0011] In the second step, gas chromatography is used to conduct qualitative and quantitative analysis of small molecular components such as hydrogen, oxygen, nitrogen and methane in crude vinyl chloride; Chromatographic conditions: Carrier gas: high-purity argon (purity is 99.999%); detector type: TCD; injection port temperature: 110℃; detector temperature: 250℃; column temperature: 50℃; chromatographic column: 3m stainless steel column (filled with 60-80 mesh 13X molecular sieve aged at 350℃); the total flow rate of the injection port gas is set to 5.999mL / min, and the flow rate of the septum purge gas is set to 3.0mL / min; the detector reference gas flow rate is set to 30.00mL / min, and the tail gas (nitrogen) flow rate is set to 5.0mL / min; chromatographic manufacturer: Agilent 7890B, USA; Standard gas: The volume percentage of hydrogen, oxygen, nitrogen and methane is 1.00%, and argon is used as the balance gas; The standard curve was prepared using the external standard method; Testing steps: Open the valve of the argon cylinder, control the outlet pressure to 0.4MPa through the pressure reducing valve, turn on the chromatographic host and computer, open the application, call out the method, and the chromatographic system automatically enters the heating program. When ready, edit the sample information, click OK, open the six-way valve, connect the aluminum foil sampling bag to the six-way valve, and start sampling; then, press the "star" key to start the run for 2 minutes; after the chromatographic run is completed, read the analysis data directly; each sample needs to be tested repeatedly, and the average value of the two tests is taken as the final analysis result; The test results are shown in the table below:

[0012] The first test showed that the hydrogen content was 7.73%, the oxygen content was 0.20%, the nitrogen content was 1.30%, and the methane content was 1.14%; The second test showed that the hydrogen content was 7.70%, the oxygen content was 0.17%, the nitrogen content was 1.17%, and the methane content was 0.98%; Reported values: Hydrogen content 7.72%, oxygen content 0.18%, nitrogen content 1.24%, methane content 1.06%; The third step is to analyze the contents of acetylene and high-boiling components in the crude vinyl chloride by gas chromatography; Chromatographic conditions: Carrier gas: high-purity nitrogen (purity is 99.999%); detector type: hydrogen flame ionization detector; column temperature: using programmed temperature rise mode, maintain at 35°C for 4.9 minutes, and then increase to 240°C at a rate of 35°C per minute and maintain for 4 minutes; detector temperature is 300°C, fuel gas flow rate is 30mL / min, practical gas flow rate is 400mL / min, and tail gas flow rate is 25mL / min; injection port temperature is 150°C, flow rate is 25mL / min, and septum purge flow rate is 3mL / min; split ratio is 8:1; chromatographic column uses capillary column: DB-624, 29m×530um×3um, flow rate is 2.2mL / min; chromatographic manufacturer: Agilent 7890A, USA; Standard gas: acetylene 2.5%; vinyl chloride, methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, trichloroethylene content are 30ppm; methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane content are 60ppm, nitrogen is used as the balance gas; Testing steps: Open the valve of the nitrogen cylinder, control the outlet pressure to 0.4MPa through the pressure reducing valve, turn on the chromatographic host and computer, open the application, call out the method, and the chromatogram automatically enters the heating program. When ready, edit the sample information, click OK, and use a 1ml glass syringe to draw 0.5ml of sample and inject it through the upper injection port; then, press the "star" key to start the run for 7.2 minutes; after the chromatographic run is completed, read the analysis data directly; each sample needs to be tested repeatedly, and the average of the two tests is taken as the final analysis result.

[0013] The test results are shown in the table below:

[0014] The first test showed that the acetylene content was 3.49% and the high-boiling substance content was 0.0171%; The second test showed that the acetylene content was 3.42% and the high boiling point content was 0.01875%; Reported values: acetylene content 3.455%, high boiling point content 0.0179%; The fourth step is to use the deduction method to subtract the contents of all components such as hydrogen, nitrogen, oxygen, methane, acetylene and high-boiling substances from 100%, and finally calculate the purity content of crude vinyl chloride. The specific results are shown in the table below:

[0015] The first test showed that the purity of crude vinyl chloride was 86.12%; The second test showed that the purity of crude vinyl chloride was 86.54%; Reported value: Purity content of crude vinyl chloride is 86.33%.

[0016] Through the detection in the examples, it can be known that the method for detecting the purity of crude vinyl chloride by gas chromatography of the present invention can accurately detect the purity content of crude vinyl chloride, and the method is simple, efficient, accurate and has good reproducibility of the detection results.

[0017] Finally, it should be noted that the above are only preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the scope of protection of the present invention.

Claims

1. A method for analyzing the purity of crude vinyl chloride in a conversion process, comprising the following steps: The first step is sampling; Features: The second step is to use chromatography to conduct qualitative and quantitative analysis of small molecular components in crude vinyl chloride; The third step is to analyze the acetylene and high boiling products in the crude vinyl chloride by chromatography; The fourth step is to calculate according to the subtraction method, and the purity of the crude vinyl chloride is obtained by deducting the content of small molecular components in the second step and acetylene and high boiling points in the third step from the total amount of crude vinyl chloride to be measured.

2. The purity analysis method for crude vinyl chloride in the conversion process according to claim 1, characterized in that: In the first step, an aluminum foil sampling bag is used for sampling. Before sampling, the aluminum foil sampling bag is evacuated and the sampling bag valve is closed. When sampling on site, the sampling valve is opened first, and then the aluminum foil sampling bag is connected to the sampling valve. The sampling valve is opened to fill the aluminum foil sampling bag, and the upper valve of the aluminum foil sampling bag and the on-site sampling valve are closed to complete the sampling work.

3. The purity analysis method for crude vinyl chloride in the conversion process according to claim 1, characterized in that: The chromatographic conditions for qualitative and quantitative analysis of small molecule components in the second step are: carrier gas: high-purity argon; detector type: TCD; injection port temperature: 110°C; detector temperature: 250°C; column temperature: 50°C; Chromatographic column: 3m stainless steel housing, filled with 60-80 mesh 13X molecular sieve aged at 350℃; the total flow rate of the inlet gas is set to 5.999mL / min, the flow rate of the septum purge gas is set to 3.0mL / min; the detector reference gas flow rate is set to 30.00mL / min, and the tail gas flow rate is set to 5.0mL / min; Standard gases include hydrogen, oxygen, nitrogen and methane, with argon as the balance gas.

4. The purity analysis method for crude vinyl chloride in the conversion process according to claim 3, characterized in that: The second step is to conduct qualitative and quantitative analysis of small molecule components as follows: open the valve of the argon cylinder, control the outlet pressure to 0.4MPa through the pressure reducing valve, open the application, the chromatograph automatically enters the heating program, and when ready, edit the sample information, open the six-way valve, connect the sampling bag to the six-way valve, and start injection; then start the run for 2 minutes; after the chromatographic run is completed, directly read the analysis data; each sample needs to be tested repeatedly, and the average value of the two tests is taken as the final analysis result.

5. The purity analysis method for crude vinyl chloride in the conversion process according to claim 3, characterized in that: In the second step, the volume percentage of standard gases: hydrogen, oxygen, nitrogen and methane are all 1.00%.

6. The method for purity analysis of crude vinyl chloride used in the conversion process according to claim 1, characterized in that: The chromatographic conditions for the analysis of acetylene and high boiling products in the third step are as follows: carrier gas: high-purity nitrogen; detector type: hydrogen flame ionization detector; column temperature: programmed temperature rise mode, 35°C for 4.9 minutes, 35°C / min to 240°C, and hold for 4 minutes; detector temperature is 300°C, fuel gas flow rate is 30mL / min, practical gas flow rate is 400mL / min, and tail gas flow rate is 25mL / min; injection port temperature is 150°C, flow rate is 25mL / min, and septum purge flow rate is 3mL / min; The split ratio is 8:1; the chromatographic column uses a capillary column: DB-624, 29m×530um×3um, and the flow rate is 2.2mL / min; Standard gases include acetylene, vinyl chloride, methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, trichloroethylene, methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane, and nitrogen as the balance gas.

7. The method for purity analysis of crude vinyl chloride used in the conversion process according to claim 6, characterized in that: The third step is to analyze acetylene and high-boiling substances as follows: open the nitrogen cylinder valve, control the outlet pressure to 0.4MPa through the pressure reducing valve, open the application, and the chromatograph automatically enters the heating program. When ready, edit the sample information, use a 1ml glass syringe to draw 0.5ml of sample and inject it through the upper injection port; then start the run for 7.2 minutes; after the chromatographic run is completed, directly read the analysis data; each sample needs to be tested repeatedly, and the average of the two tests is taken as the final analysis result.

8. The method for purity analysis of crude vinyl chloride used in the conversion process according to claim 6, characterized in that: The standard gas in the third step: the acetylene content is 2.5%; the content of vinyl chloride, methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, and trichloroethylene is 30ppm; the content of methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, and 1,2-dichloroethane is 60ppm.

9. The method for purity analysis of crude vinyl chloride used in the conversion process according to claim 1, characterized in that: The standard curve was prepared using the external standard method.

10. The purity analysis method for crude vinyl chloride in the conversion process according to claim 1, characterized in that: High boiling substances include the sum of methyl bromide, vinyl bromide, trans-dichloroethylene, cis-dichloroethylene, trichloroethylene, methyl chloride, acetaldehyde, ethyl chloride, 1,1-dichloroethylene, 1,1-dichloroethane, and 1,2-dichloroethane.

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